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Where did they go today?

By Sebastian Moericke-Kreutz
on July 30, 2000

Have you ever wondered where people go when they leave your site? With php3 it is easy to trace this.
Sure, several solutions of redirect-cgi’s exist, but why bother with another language when
you can keep it straight to php3 and make it more comfortable?
My setting for writing this from scratch was a site where I had multiple pages with identical
links in a part of them, but I’d wanted to know the use of the external links in detail: Who
left where from which page and when. So here is how it works:
When you read the documentation about php3 in detail, you may have come across this kind of
<?php Header("Location: http://www.php.net"); exit; ?>

You find it in Section XIV. It uses a HTTP redirect command to make the users browser access a new
location. This is a good example how simple things in PHP3 can be: We will expand it, so that
we make a suitable tool for the curious ;).
First we make targeting more flexible, it is the ‘where’. This one is easy, because you just
add a parameter to the URL of the redirector page. I’ll call it
<?php '$u_target' ?>

(u_ stands for URI/URL, this is a personal way to determine where the variable belongs to that I am using.
Others: db_ is for database , p_ for page , f_ for function and so on.)
Then we want to record from ‘which’ page the link was activated. Since the referrer-information
is sometimes filtered out by proxies, browsers and firewalls, we will use the additional variable

<?php '$u_referrer' ?>

for this purpose. You can use simple keywords like
‘homepage’, the name of the page example.html or the full address “http://…”. It doesn’t really matter,
but keywords are better to understand on first look. When you skip this parameter,

<?php $HTTP_REFERER ?>

is used automatically.
Note that if it doesn’t exist either,
<?php '$u_referrer' ?>

will be set to ‘none’.
We will determine the “who” by using server-variables. We’ll take
<?php $REMOTE_ADDR ?>

address for
this purpose, since Apache and IIS deliver it in nearly 90% of all installations ;).
<?php $REMOTE_HOST ?>

is better but since DNS-lookup is switched off sometimes, you’ll have to try out on your server
yourself. (Use
<?php phpinfo() ?>

for this purpose. It’s tip I got from Tim and others
which lead also to this script. Thanks 😉
‘When’ is easy:
<?php time() ?>

is all we need.
Logging the information gathered to a database is the method of choice. Since the data-structure
is simple and flat, you should be able to use any kind of solutions – even plain text files will
do it. Since MySQL is nice for this job, we’ll take it for our purpose.
Since this article focuses on redirecting, I will keep the part of information exchange with the
database brief. You’ll find more information on this topic here in phpbuilder.com and on the web.
Here is the SQL-Command for creating the table in MySQL:
# Definition
# Table structure for table 'redirect'
CREATE TABLE redirect (
  target varchar(80) DEFAULT 'no target' NOT NULL,
  referrer varchar(80) DEFAULT 'none' NOT NULL,
  client varchar(40) DEFAULT 'no client' NOT NULL,
  timeused datetime DEFAULT '0000-00-00 00:00:00' NOT NULL